<template>
    <div class="pagination">
        <button :disabled="pageNo == 1" @click="postPageNo(pageNo - 1)">上一页</button>
        <button v-if="startNumAndendNum.start > 1" @click="postPageNo(1)" :class="{active: pageNo == 1}">1</button>
        <button v-if="startNumAndendNum.start > 2">···</button>
        <!-- 中间部分，v-for也可以遍历数字，从1开始 -->
        <button v-for="(item, index) in startNumAndendNum.end" v-if="item >= startNumAndendNum.start"
            @click="postPageNo(item)" :class="{active: pageNo == item}">{{item}}</button>

        <button v-if="startNumAndendNum.end < totalPage - 1">···</button>
        <button v-if="startNumAndendNum.end < totalPage" @click="postPageNo(totalPage)"
            :class="{active: pageNo == totalPage}">{{totalPage}}</button>
        <button :disabled="pageNo == totalPage" @click="postPageNo(pageNo + 1)">下一页</button>

        <button style="margin-left: 30px">共 {{total}} 条</button>
    </div>
</template>
  
<script>
export default {
    name: "Pagination",
    props: ['pageNo', 'pageSize', 'total', 'continues'],
    methods: {
        postPageNo(pageNo) {
            this.$emit('getPageNo', pageNo);
        }
    },
    computed: {
        totalPage() {
            // 向上取整Math.ceil
            return Math.ceil(this.total / this.pageSize)
        },
        startNumAndendNum() {
            let start = 0, end = 0;
            if (this.continues > this.totalPage) {
                start = 1;
                end = this.totalPage
            } else {
                start = this.pageNo - Math.floor(this.continues / 2);
                end = this.pageNo + Math.floor(this.continues / 2);
                if (start < 1) {
                    start = 1;
                    end = this.continues
                }
                if (end > this.totalPage) {
                    end = this.totalPage
                    start = this.totalPage - this.continues + 1;
                }
            }
            return {
                start,
                end
            }
        }
    }
}
</script>
  
<style lang="less" scoped>
.pagination {
    text-align: center;

    button {
        margin: 0 5px;
        background-color: #f4f4f5;
        color: #606266;
        outline: none;
        border-radius: 2px;
        padding: 0 4px;
        vertical-align: top;
        display: inline-block;
        font-size: 13px;
        min-width: 35.5px;
        height: 28px;
        line-height: 28px;
        cursor: pointer;
        box-sizing: border-box;
        text-align: center;
        border: 0;

        &[disabled] {
            color: #c0c4cc;
            cursor: not-allowed;
        }

        &.active {
            cursor: not-allowed;
            background-color: #409eff;
            color: #fff;
        }
    }
}
</style>
  